1. Field of the Invention
The invention relates to an electric actuator system for hospital and care beds.
2. the Prior Art
The actuator system is according to the invention of the type which can be used for adjusting a hospital or care bed. In this type of bed the mattress is carried by a support surface having an adjustable backrest and legrest section, said support surface being mounted in a bed frame which may be raised and lowered by means of linear actuators in the actuator system. Further, the backrest and legrest sections of the bed may be adjusted by means of linear actuators. Normally, a type of linear actuator comprising a thrust rod, e.g. of the type described in WO 02/29284 A1 Linak A/S is used. This type of linear actuator (see also FIGS. 5 and 6) comprises a spindle with a spindle nut. The spindle is driven by a reversible electric motor through a transmission. When the spindle is driven, the spindle nut is moved in an inwards or outwards direction depending on the direction of rotation of the electric motor. The linear actuator is a separate product with the spindle, transmission and electric motor enclosed in a housing. The housing typically consists of a motor housing and an outer tube. An inner tube is secured to the spindle nut. The inner tube is displaced in and out of the outer tube as the spindle nut is moved in and out on the spindle. In the opposite end of the spindle nut the inner tube comprises a front mounting. The outer side of the motor housing is furnished with a rear mounting. The front mounting and rear mounting are used to secure the linear actuator in the structure which should be adjusted.
For certain patients in the hospital and care sector it is necessary for the nursing staff to know whether the patient is in the process of leaving his bed or has left his bed. Such a bed is i.a. described in U.S. Pat. No. 4,934,468 Hill Rom Co. Inc. and U.S. Pat. No. 5,276,432 Stryker Corp. These hospital beds are equipped with a weighing system for weighing and/or monitoring the patient's weight. The weighing system can however also be configured to monitor the patient's position in the bed. The weighing system can further be connected to an alarm which can give off a signal in case the patient assumes a position where it is conceivable that the patient may leave the bed or has already left the bed. A bed having similar characteristics is described in EP 1 974 708 A1 Paramount. Here, changes in the patient's center of gravity are registered by a number of interconnected weight sensors, located at each corner of the lying surface of the bed. By comparing the readings from each weight sensor, it can be detected whether a patient is sitting up and is thus potentially in the process of leaving the hospital bed, but naturally also whether the patient has left the bed.
Common for these types of bed structures is that they are intended for continuous weighing for accurate supervision of the patient's weight. In order to be able to do this with a sufficient accuracy, high-end sensors with a high resolution are used. This fact is thus also reflected in the price of these bed structures, which are very expensive. The use of these beds is thus also limited to a select few patients requiring special treatment and special care.
For care of patients, e.g., during the night, it has proven expedient to provide one or more orientation lights under the bed (Under Bed Light). The orientation light is both used by the users to navigate around the room when getting out of bed in the dark and by the staff to navigate around the room without having to turn on the ceiling light and thus disturbing the other bedbound patients. As an example, U.S. Pat. No. 6,234,642 B1 Dewert can be mentioned, where the orientation light of the bed is connected to the control box. Here, a sensor in the mattress of the bed can be connected to the control box such that the light in the control box is turned on when the patient sits up or has left the bed. The principle of having light under the bed where the activation thereof is linked to the user of the bed is known as far back as, e.g., U.S. Pat. No. 2,185,051 O. J. Daigle. This document discloses a bed which in connection with the lying surface comprises one or more switches which, if desired, can be connected in such a manner that a light source placed under the bed is turned on when the person, e.g., leaves the bed.
Activation of the orientation light under the bed by means of sensors in the mattress is however undesired as they often, and especially after continuous use, can give off faulty signals or signals may fail to appear. Although the signal for activation of the light could be provided by the beds comprising weight sensors described above, this would however represent a relatively expensive solution.
In addition to the orientation light located under the bed, it is known from EP 1 275 896 A1 Deapillat to integrate a light strip in the floor running from each bed in a shared bed room to a common bathroom. If a patient sits up in the bed or leaves the bed in the night, this is registered by a motion sensor located next to the bed. The motion sensor, which may, e.g., be an infrared sensor, gives off a signal to turn on both the light under the bed, in the light strip in the floor as well as in the bathroom. This ensures that the patient can find his way to the bathroom without disturbing the other patients in the bed room. The use of motion sensors is however undesired since the movement of other people in the room could cause unintended activation of the light. Furthermore, the integration of a light source in the floor is subject to a number of expenses. Further, the application of the room is limited as it is bound by the location of the light strip in the floor.
It is thus desired to provide an actuator system for a hospital or care bed which represents a simpler, more reliable and cheaper alternative for activating the orientation light, both in connection with the bed as well as in the proximity of the bed.